I mentioned I'd like a Magnetic Theft effect in the set, and I think I still would. But I also want some kind of permanent control-change effect for an Equipment. I think that ought to be blue, as it's Carry Away meets Aura Graft.

Could be an instant, but though this set wants a higher-than-usual level of instants, MaRo has been clear in the past that you don't want everything to happen at instant speed.

Technically this can target an Aura with enchant player (e.g. Curse of Exhaustion) or enchant land (Fertile Ground). It won't normally do much, as the "attach to a creature you control" clause will fail to do anything. I'd rather leave the simpler wording rather than try to spell out "Aura with enchant creature or enchant permanent" (which still fails to get Encrust, Wurmweaver Coil etc). I don't want to go with Aura Graft's "that's attached to a permanent" wording either, because the moment in the series this best matches is when Lelouch makes off with the prototype Gawain IFX-V301, which was on a deserted island, most definitely not "attached to a creature".

I think it would be better to make this one an Aura with "enchant Equipment or Aura", with an ETB ability to change what the enchanted thing is attached to. For Auras, 99% of time it doesn't matter who controls it, but that's important for Equipment due to the Equip ability.

...You're right, this probably should itself be an Aura (like Carry Away was). Very sensible suggestion, thank you.

I wonder if it might be problematic to bypass Equip costs? Probably not - Kor Outfitter did that at common at 2 mana, so I'm sure that's fine.